How to use Nextcloud Talk / Spreedme for Video Online Consulting

I am just thinking about using “Nextcloud spreedme” (or Nextcloud talk?) to establish a video online consulting service. But I have no idea, how to setup Nextcloud for this task. And I don’t know, how to connect to clients.

I have just tested the messenger “Wire” for this purpose and it seems, that it does, what I want and I would like to have Nextcloud, performing similar to Wire:

  1. A client wants to have a consultation. (he contacts me via email or phonecall)

  2. I send him a link via email, so that he can connect to my Nextcloud server via webRTC capable Browser.

  3. I get his call, when he clicks the link, opening the Nextcloud site in his browser and I will accept his call in my browser or in my Nextcloud App.

  4. Video-call connection is established and consulting may start now.

  5. It’s of great importance, that my clients should not have to install any software on their device, in order to share video-telephonie and simply can use webRTC via adequate browsers.

Due to security reasons I want to limit connections to webRTC, as no port on the router of my clients or on my router has to be open / listening.

I have not found any manual or instruction on Nextcloud website, where this information is offered.

What will I have to do, to establish this functionality with my Nextcloud installation?

Thank you for your patience with my lack of knowledge!
Kind regards